Method of and structure for fixing a flexible electrical conductor

ABSTRACT

A method of fixing a flexible electrical conductor, in which a plurality of flat conductors in which their connecting ends to be connected to another circuit are exposed are integrally covered with a resin-made cladding member, to a fixing portion for connection to the other circuit, comprises the steps of: placing the cladding member on this side of the connecting ends on the fixing portion; and welding together the cladding member on this side of the connecting ends and the fixing portion so as to fix the flexible electrical conductor to the fixing portion. As a result, even if an external force is applied to the flexible electrical conductor, the force is not applied directly to a connecting portion for connecting the connecting ends to connecting ends of the other circuit, thereby improving the electrical reliability in the connection.

This is a division of application Ser. No. 09/106,044, filed Jun. 29,1998, U.S. Pat. No. 6,156,138 which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a method of and a structure for fixinga flexible electrical conductor, in which a plurality of electricalconductors are covered with a resin-made cladding member, to a fixingportion for connection to another circuit.

FIGS. 1 and 2 respectively show connecting portions 1 and 3 of flatelectric wires (flexible electrical conductors) disclosed in JapaneseUtility Model Application Laid-Open No. 30723/1991, as well as aflexible electrical conductor 5 connected to the connecting portion 1 or3.

In the connecting portion 1 shown in FIG. 1, a step portion 7 is formedat a distal end portion, and connecting terminals 9 are exposed on thisstep portion 7. A pair of positioning holes 11 are formed at a distalend portion of the step portion 7. Meanwhile, the flexible electricalconductor 5 connected to this connecting portion 1 is covered with acladding member 15 in which distal end portions of three flat conductors13 are exposed. A pair of through holes 17 are formed in an end portionof the cladding member 15. A pair of fixing pins 21 of a fixing cover 19are inserted in the through holes 17.

In a case where the flat conductors 13 of the flexible electricalconductor 5 are connected to the connecting terminals 9, the flexibleelectrical conductor 5 is placed on the step portion 7, and after theflat conductors 13 are superposed on the connecting terminals 9, thefixing pins 21 of the fixing cover 19 are inserted into the throughholes 17 and the positioning holes 11. Next, distal end portions of thefixing pins 21 which passed through the positioning holes 11 andprojected to the reverse side are caulked by heating. Consequently, theflexible electrical conductor 5 is nipped by the fixing cover 19 and thestep portion 7, thereby allowing the flat conductors 13 to beelectrically connected to the connecting terminals 9.

On the other hand, in the connecting portion 3 shown in FIG. 2, a pairof fixing pins 23 are provided projectingly on a distal end portion ofthe step portion 7. When the flexible electrical conductor 5 is placedon the step portion 7, the fixing pins 23 are inserted into the throughholes 17, and after a fixing cover 25 is placed on top of the flexibleelectrical conductor 5, the fixing pins 23 are inserted into a pair ofpositioning pins 27 in the fixing cover 25. Next, distal end portions ofthe fixing pins 23 which projected from the positioning holes 27 of thefixing cover 25 are caulked by heating. Consequently, the flexibleelectrical conductor 5 is nipped by the fixing cover 25 and the stepportion 7, thereby allowing the flat conductors 13 to be electricallyconnected to the connecting terminals 9.

In the case where the flexible electrical conductor 5 is connected tothe aforementioned connecting portion 1 or 3, the cladding member 15 isnipped by the fixing cover 19 or 15 and the step portion 7 in which thelongitudinal offset is prevented by the fixing pins 21 or 23, and theflat conductors 13 are electrically connected to the connectingterminals 9.

In the connecting portion 1 or 3, the positioning of the flat conductors13 and the connecting conductors is effected by inserting the fixingpins 21 or 23 into the through holes 17.

However, there is a problem in that, in the aforementioned connectingportion 1 or 3, if the caulked portions of the fixing pins 21 or 23become loose, play occurs between the fixing cover 19 or 25 and the stepportion 7, and the state of close contact deteriorates, with the resultthat the electrical reliability in the connection declines.

In addition, if a force moving in the axial direction away from theconnecting portion 1 or 3 is applied to the flexible electricalconductor 5, that force is concentrated on the fixing pins 21 or 23, theforce is applied locally to the cladding member 15. For this reason,there is a possibility that the cladding member breaks. Further, if theforce moving in the axial direction away from the connecting portion 1or 3 is applied, the force is applied directly to the connecting portion1 or 3, so that there is a possibility that the flat conductors 13 andthe connecting terminals 9 may offset from each other. As a result, thereliability in electrical connection declines.

Furthermore, there is a problem in that when the flexible electricalconductor 5 is connected to the connecting portion 1 or 3, the fixingcover 19 or 25 is required, so that the number of component parts usedincreases, resulting in higher cost.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide amethod of and a structure for fixing a flexible electrical conductorwhich make it possible to prevent the deterioration of the state ofclose contact between the electrical conductor and connecting terminalsof another circuit, which make it possible to prevent an external force,if applied, from being applied directly to the portion connected to aconnecting portion of another circuit, and which make it possible toreduce the number of component parts used.

To this end, in accordance with a first aspect of the present invention,there is provided a method of fixing a flexible electrical conductor, inwhich a plurality of flat conductors in which their connecting ends tobe connected to another circuit are exposed are integrally covered witha resin-made cladding member, to a fixing portion for connection to theother circuit, comprising the steps of: placing the cladding member onthis side of the connecting ends on the fixing portion; and weldingtogether the cladding member on this side of the connecting ends and thefixing portion so as to fix the flexible electrical conductor to thefixing portion.

In accordance with the first aspect of the invention, after the claddingmember on this side of the connecting ends of the flexible electricalconductor is placed on the fixing portion, the cladding member on thisside of the connecting ends and the fixing portion are welded together.As a result, the flexible electrical conductor is fixed to the fixingportion. In this case, since the cladding member on this side of theconnecting ends is welded to the fixing portion, an external forceapplied to the flexible electrical conductor is not transmitted directlyto the connecting ends and the connecting portion, with the result thatthe connecting ends and the connecting ends of another circuit areprevented from offsetting from each other.

In accordance with a second aspect of the present invention, in themethod of fixing a flexible electrical conductor according to the firstaspect of the invention, in which the cladding member on this side ofthe connecting ends is placed on the fixing portion in close contacttherewith, ultrasonic vibrations are applied to the cladding member onthis side of the connecting ends and the fixing portion so as to effectwelding.

In accordance with the second aspect of the invention, in the state inwhich the cladding member on this side of the connecting ends is placedon the fixing portion in close contact therewith, ultrasonic vibrationsare applied to the cladding member on this side of the connecting endsand the fixing portion. Consequently, the cladding member and the fixingportion are welded together, thereby allowing the flexible electricalconductor to be fixed to the fixing portion.

In accordance with a third aspect of the present invention, in themethod of fixing a flexible electrical conductor according to the firstor second aspect of the invention, an irregular surface portion isprovided on the fixing portion along a direction perpendicular to alongitudinal direction of the flat conductors.

In accordance with the third aspect of the invention, the claddingmember on this side of the connecting ends is placed on the irregularsurface portion provided on the fixing portion along a directionperpendicular to the longitudinal direction of the flat conductors, andthis irregular surface portion and the cladding member are weldedtogether. In this case, by virtue of the provision of the irregularsurface portion on the fixing portion, the area of contact between thecladding member and the fixing portion becomes large.

In accordance with a fourth aspect of the present invention, in themethod of fixing a flexible electrical conductor according to any one ofthe first to third aspects of the invention, in state in which theplurality of flat conductors which are elongated are arranged planarlysubstantially planarly at predetermined intervals, the flexibleelectrical conductor is covered with the resin-made cladding member.

In accordance with the fourth aspect of the invention, since theresinous cladding member which covers the plurality of flat conductorsarranged planarly substantially in parallel at predetermined intervalsis welded to the fixing portion, the flexible electrical conductor isfixed to the fixing portion. In this case, even if an external force isapplied to the flexible electrical conductor along its longitudinaldirection, the external force is applied to the overall welded portionof the welded cladding member, and the force is not applied directly tothe connecting portion correcting the conductors and the other circuit.

In accordance with a fifth aspect of the present invention, there isprovided a structure for fixing a flexible electrical conductor, inwhich a plurality of flat conductors in which their connecting ends tobe connected to another circuit are exposed are integrally covered witha resin-made cladding member, to a fixing portion for connection to theother circuit, wherein the cladding member on this side of theconnecting ends is welded to the fixing portion.

In accordance with the fifth aspect of the invention, the claddingmember on this side of the connecting ends is welded to the fixingportion so as to fix the flexible electrical conductor to the fixingportion.

In accordance with a sixth aspect of the present invention, in thestructure for fixing a flexible electrical conductor according to thefifth aspect of the invention, an irregular surface portion is providedon the fixing portion.

In accordance with the sixth aspect of the invention, since theirregular surface portion is provided on the fixing portion, the weldingarea between the cladding member on this side of the connecting ends andthe fixing portion becomes large.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription of the invention when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a conventional method of and astructure for fixing a flexible electrical conductor;

FIG. 2 is a perspective view illustrating a another conventional methodof and a structure for fixing a flexible electrical conductor;

FIGS. 3(a) and 3(b) are diagrams illustrating a first embodiment of amethod of fixing a flexible electrical conductor in accordance with thepresent invention, in which

FIG. 3(a) is a perspective view of the flexible electrical conductor anda fixing portion, and FIG. 3(b) is a cross-sectional view thereof;

FIG. 4 is an exploded perspective view illustrating a fixing portion anda flexible electrical conductor which is fixed to the fixing portion ina second embodiment of the method of fixing a flexible electricalconductor in accordance with the present invention;

FIG. 5 is a plan view illustrating the fixing portion and the flexibleelectrical conductor which is fixed to the fixing portion in accordancewith the second embodiment; and

FIG. 6 is a cross-sectional view illustrating the fixing portion and theflexible electrical conductor which is fixed to the fixing portion inaccordance with the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the accompanying drawings, a description will be givenof embodiments of the structure for a method of fixing a flexibleelectrical conductor in accordance with the present invention.

First Embodiment

FIGS. 3(a) and 1(b) show a flexible electrical conductor 29 and a fixingportion 31 made of PBT (polybutylene terephtalate) or the like inaccordance with a first embodiment. FIG. 3(a) is a perspective view ofthe flexible electrical conductor 29 and the fixing portion 31 to whichthis flexible electrical conductor 29 is fixed, while FIG. 3(b) is across-sectional view illustrating a state in which the flexibleelectrical conductor 29 is welded to the fixing portion 31.

As shown in FIGS. 3(a) and 3(b), the flexible electrical conductor 29 isarranged such that three elongated flat conductors 33 are arrangedplanarly substantially parallel to each other at predeterminedintervals, and are covered with a resin-made cladding member 35. Distalend portions of the flat conductors 33 are exposed to form connectingterminals 37. These connecting terminals 37 are connected to connectingterminals 39 of another circuit. The cladding member 35 on this side ofthe connecting terminals 37 is formed as a welding portion 41 which iswelded to the fixing portion 31.

The fixing portion 31 has an irregular surface portion 43 in which aserrated formation is arranged along a direction perpendicular to thelongitudinal direction of the flat conductors 33 (the axial direction ofthe fixing portion 31). This irregular surface portion 43 is comprisedof four angular edges 45 and notches 47 provided between adjacent onesof the angular edges 45 and on outer sides of the outermost angularedges 45. In the state in which the welding portion 41 is welded ontothe fixing portion 31, the flat conductors 33 are superposed on theconnecting terminals 39 of the other circuit in contact therewith, andare electrically connected thereto.

Next, a description will be given a method of fixing the flexibleelectrical conductor 29 to the fixing portion 31.

First, after the welding portion 41 on this side of the connectingterminals 37 is placed on the fixing portion 31, the welding portion 41and the fixing portion 31 are welded to each other. In this case, inwhich the edges 45 of the irregular surface portion 43 abut against thecladding member 35 between the flat conductors 33, the welding portion41 and the fixing portion 31 are welded to each other by applying heator ultrasonic vibrations to the fixing portion 31 and the claddingmember 35. In this case, since the welding portion 41 is welded in closecontact with the irregular surface portion 43, the welding portion 41also assumes a serrated form. Thus the flexible electrical conductor isfixed to the fixing portion 31. In this state, the connecting terminals37 are superposed in close contact with the connecting terminals 39 ofthe other circuit, and are electrically connected thereto.

In accordance with this embodiment, since the welding portion 41 iswelded directly to the fixing portion 31, the connecting terminals 37and the connecting terminals 39 of the other circuit are superposed ontop of each other in close contact. In addition, an external forceapplied to the flexible electrical conductor 29 is not transmitted tothe portion connecting the connecting terminals 37 and the connectingterminals 39 of the other circuit. Further, since the external forceapplied to the flexible electrical conductor is not applied locally tothe cladding member 35, the cladding member does not break. Accordingly,it is possible to improve the electrical reliability in t he connection.

Further, since the welding portion 41 of the cladding member 35 iswelded directly to the fixing portion 31, the state of close contactbetween the connecting terminals 37 and the connecting terminals 39 ofthe other circuit does not deteriorate.

Furthermore, in this embodiment, since the fixing portion 31 is providedwith the irregular surface portion 43, and the cladding member 35 iswelded directly to this irregular surface portion 43, it is possible tosecure a large welded area without enlarging the width of the fixingportion 31. Therefore, the welding portion 41 can be fixed more firmlyto the fixing portion 31.

That is, although if the fixing portion 31 is planar, an area forwelding the welding portion 41 of the cladding member 35 is required bythe portion of the widthwise length of the flexible electrical conductor29, the width of the fixing portion 31 can be made shorter than thewidth of the flexible electrical conductor 29 by providing the irregularsurface portion 43.

Further, since the irregular surface portion 43 is provided along thewidthwise direction of the fixing portion 31, even if an external forceis applied in the widthwise direction, the flexible electrical conductor29 is difficult to be offset in the widthwise direction, so that theconnecting terminals 37 are not offset from the connecting terminals 39of the other circuit.

Further, since it is unnecessary to fix the flexible electricalconductor 29 by means of a fixing plate in the conventional manner, thenumber of component parts used can be reduced, thereby making itpossible to lower the manufacturing cost.

Second Embodiment

Next, a description will be given of a second embodiment. This secondembodiment is a fixing method which is used in fixing a terminal portionof a flexible electrical conductor 49 arranged between a steering wheeland a steering shaft of an automobile to a cable reel (not shown). FIG.4 is a exploded perspective view illustrating a terminal fixing member51 for fixing terminals of the cable reel as well as the flexibleelectrical conductor 49 which is fixed to the terminal fixing member 51.

As shown in FIG. 3, the terminal fixing member 51 is formed in anarcuate shape in terms of its overall configuration, and a retainingportion 53 for retaining connecting terminals (not shown) of anothercircuit is provided at a distal end portion thereof. The retainingportion 53 has three rectangular hole portions 55 formed in such amanner as to penetrate the terminal fixing member 51 from its obverseside to its reverse side. The connecting terminals 37 of the flexibleelectrical conductor 49 are placed on these hole portions 55. A fixingportion 57 for fixing the flexible electrical conductor 49 is formed onthis side of the retaining portion 53.

The fixing portion 57 has an irregular surface portion 61 formed on aplanar upper surface 59. The irregular surface portion 61 is comprisedof a pair of angular projections 63 provided on transverse oppositesides of the fixing portion 57 in such a manner as to project from theupper surface 59, as well as a pair of notched projections 65 arrangedat equal intervals between the pair of angular projections 63 and eachhaving a substantially M-shaped outer configuration in terms of itscross section. The two projecting edges of each of the pair of notchedprojections 65 are also formed as a pair of angular projections 63, andrecessed portions 67 are formed on transverse opposite sides of thefixing portion 57 and between adjacent ones of all the angularprojections 63. Furthermore, as shown in FIGS. 5 and 6, the weldingportion 41 of the flexible electrical conductor 49 is welded to theirregular surface portion 61. In this case, as shown in FIG. 5, thewelding portion 41 is welded to the fixing portion 57 by thermal weldingor ultrasonic vibration welding such that the angular projections 63 arerespectively positioned at portions of the cladding member 35 that arelocated between the flat conductors 33 and on outer sides of theoutermost flat conductors 33.

It should be noted that, in FIG. 4, reference numeral 69 denotes a coverfor covering the retaining portion 53 and the fixing portion 57. Thiscover 69 does not serve to fix the flexible electrical conductor 49 tothe fixing portion 57, but merely covers the retaining portion 53 andthe fixing portion 57 from the outside.

To fix the flexible electrical conductor 49 to the fixing portion 57,the welding portion 41 of the flexible electrical conductor 49 is firstplaced on the fixing portion 57. In this state, the exposed connectingterminals 37 are located above the hole portions 55 of the retainingportion 53. Next, by applying heat or ultrasonic vibrations to theirregular surface portion 61 and the welding portion 41, the weldingportion 41 is welded to the fixing portion 57, as shown in FIG. 6. As aresult, the flexible electrical conductor 49 is fixed to the fixingportion 57.

In accordance with this embodiment, since the fixing portion 57 iswelded directly to the welding portion 41, an external force applied tothe flexible electrical conductor 49 is not transmitted directly to theconnecting portion for connecting the connecting terminals 37 and theconnecting terminals of the other circuit. Consequently, it is possibleto improve the electrical reliability in the connection.

In addition, since it is unnecessary to fix the flexible electricalconductor 49 by means of a fixing plate in the conventional manner, thenumber of component parts used can be reduced, thereby making itpossible to lower the manufacturing cost.

It should be noted that in a case where the welding portion 41 and thefixing portion 57 are welded together, the welding portion 41 and thefixing portion 57 may be welded together by a method other than weldingby using heat or welding by using ultrasonic vibrations.

While there has been described in connection with the preferredembodiment of the invention, it will be obvious to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the invention, and it is aimed, therefore, to cover inthe appended claim all such changes and modifications as fall within thetrue spirit and scope of the invention.

What is claimed is:
 1. A fixing structure comprising: a flexibleelectrical conductor having a plurality of flat conductors integrallycovered with a resin-made cladding member and also having connectingends that are connectable to another circuit and at which said pluralityof flat conductors are exposed; and a fixing portion for connection tosaid another circuit, wherein a portion of said cladding member that isbetween the plurality of flat conductors is welded to said fixingportion and wherein an irregular surface portion is provided on saidfixing portion.